In order to lower the cost, many products like chip-array ball grid array (CA BGA) adopt a matrix form in their basic designs. Conventionally, a matrix substrate must adopt a common-electrode type electroplated wires. As shown in FIG. 1, electroplated wires 14 are pulled to a common electrode 15 from gold fingers 12 on the front surface of a matrix substrate 10 so that electroplating can be proceeded for the gold fingers 12. Limited by the manufacturing capability of substrate, however, it is necessary to take into account the distance from a solder mask opening 17 to a package edge 16. Because a distance 13 of at least 150μm from the gold fingers 12 to the package edge 16 is required, the flexibility of substrate layout is limited. Moreover, a distance L1 from the gold fingers 12 to a chip 18 needs to shrink therewith. If this distance L1 is close to a minimum value of 450 μm for wire bonding, the yield of wire bonding will be reduced.
In order to solve the above space problem in substrate layout, as shown in FIG. 2, the distance from the solder mask opening 17 to the package edge 16 isn't taken into account. Although a solder resist distance 19 shown in FIG. 1 can be saved in this method, invasion of moisture may occur to reduce the reliability of product.
In order to solve the above problem, another process with no electroplated wire has been derived. As shown in FIG. 3, electroplating can be performed to the gold fingers 12 without pulling the electroplated wires 14 from the gold fingers 12. Therefore, the distance from the gold fingers 12 to the package edge 16 only needs to consider the alignment tolerance and a distance from the solder mask opening 17 to the gold fingers 12. The flexibility in design thus increases much. Although the reliability can be enhanced without extending the electroplated wires 14 to the package edge 16, however, the cost of a matrix substrate with no electroplated wire is high.
Accordingly, the present invention aims to provide an electroplated wire layout for package sawing to solve the above problems in the prior art.